To terraform a planet is to change its environment, making it livable for humans and other Earth-based life forms. Most life on Earth could not survive on Mars today. Even the hardiest bacteria would soon shrivel and die from the high radiation exposure, extreme cold, or other martian hazard. If humans want to maintain a long-term presence on Mars, building cities and establishing civilizations, terraforming would be one way to make that possible.

"We want to find out about Mars life before we take Earth life to a place where it can be modifying the environment in a way that we can’t control," said NASA’s Planetary Protection Officer, John Rummel.

Mars currently has a very thin carbon dioxide atmosphere. The average air pressure on Earth is one hundred times greater than the air pressure on Mars. To introduce adequate oxygen and increase the atmospheric pressure enough to suit humans would take at least 40,000 Earth years, and perhaps as long as 4 million years.

When author Kim Stanley Robinson was writing his novel, "Red Mars," he was surprised to find that many people favored leaving Mars alone, in its current, pristine state, unsullied by the works of man. "I had some sympathy for (that position), because I like rocky places myself," said Robinson. "If somebody proposed irrigating and putting forests in Death Valley, I would think of this as a travesty."

Astrobiology Magazine had the opportunity to listen in on a conversation between science-fiction author Kim Stanley Robinson and NASA’s John Rummel about planetary contamination.

Kim Stanley Robinson (KSR): Now tell me, what’s your field of expertise? What do you study?

John Rummel (JR): I don’t have any expertise – I work at NASA Headquarters.

KSR: Oh, you’re the…

JR: I’m the Planetary Protection Officer.

Donna Shirley: John, your job is to protect planets, and Stan has envisioned a future where there are people running all over the planet Mars. Do you think that’s incompatible?

JR: Not at all. In fact, the reason that there’s a job to protect the planets is so we have the options of running all over the place later on. If there’s life on Mars, we want to know about it before we blunder into a situation that we can’t control, and that might in fact be dangerous to Earth.

KSR: What about the several or many thousands of bacteria that are already on Mars, because of our Landers?

JR: I hope that there’s more than that. The fact is that the surface of Mars appears to be inimical to life as we know it — on the surface, and as long as you stay in the highly ultraviolet radiated places. And in the long term, galactic cosmic radiation takes care of a certain amount of things. But now we’re just getting a good inkling for those deep down, really wonderful spots on Mars that might still exist.

KSR: But what about the crash sites, where essentially a Lander has augered in, and perhaps gone in some meters?

JR: Actually when you auger in on Mars, depending on what the soil is like at the place, you’ll probably will only go down about a meter or so. And basic crash sites where you have an integrated vehicle, all that probably stays exposed to the UV anyway.

KSR: Right.

JR: What we worry about, of course, are penetraters and other things that might go down farther than a meter and a half or more. The (Deep Space-2) DS-2 probes worry me much more than the Mars Polar Lander, because they did go down in a way that may have been unconstrained.

KSR: Aren’t we kind of caught in a catch-22, like with Lake Vostak, where, in order to try to find out if there is deep level indigenous life on Mars, our instruments of examination – the drills – will themselves be sources of contamination? Is there any way out of this catch-22?

I think it’s possible to do the experiment to a level of probability that is less than one. I think we can actually envision examining Mars for signs of life without contaminating it, but we have to realize that if we examine it at all – if we launch anything to Mars – we have the chance of contaminating it. But not more so than probably the chance that Mars would get contaminated naturally by a large impact event that would take material from Earth to Mars today.

KSR: Which has happened many times.

JR: It’s happened many times, and it may happen in the future. It’s one of the reasons we (should) talk about terraforming. One of the things that we want to think about is having another home for the human species off of this planet, in a way that will give us an opportunity to survive as a civilization that kind of an impact.